PC doesn’t appear in WSUS Unassigned Computers

I have been using WSUS successfully for a long time to update PC’s

I am trying to get an old HP D510 to update from WSUS. I have treated this PC the same as all the others.

I have added PC to WSUS group policy. Usually the PC will appear in Unassigned Computers group in WSUS, where I can then assign it to a group. However it won’t appear.

I can see in Automatic Updates that PC has received Group Policy settings from AD, and from local machine tried gpupdate /force, reboots etc etc…

Any ideas would be greatly appreciated

Many thanks